Oral Loading Dose of Amiodarone
The oral loading dose of amiodarone is 800 to 1,600 mg per day in divided doses until a total of 10 g has been given for ventricular arrhythmias, or 600 to 800 mg per day in divided doses until a total of 10 g has been given for atrial fibrillation. 1
Dosing Regimen by Indication
Ventricular Arrhythmias
- Initial loading: 800-1,600 mg/day in divided doses
- Continue until total of 10 g has been administered (approximately 1-2 weeks)
- Maintenance: 200-400 mg/day 1
Atrial Fibrillation
- Initial loading: 600-800 mg/day in divided doses
- Continue until total of 10 g has been administered
- Higher initial dosages or IV dosing may be used in unstable inpatients
- Maintenance: 200 mg/day 1
Transition from IV to Oral Therapy
When converting from intravenous to oral amiodarone, the oral loading dose should be adjusted based on the duration of previous IV therapy:
- IV therapy <1 week: 800-1,600 mg oral amiodarone daily
- IV therapy 1-3 weeks: 600-800 mg oral amiodarone daily
- IV therapy >3 weeks: 400 mg oral amiodarone daily 1, 2
Administration Considerations
- Oral doses should be given in divided doses (typically twice daily during loading)
- Loading doses should be administered with food to minimize gastrointestinal side effects
- Potassium and magnesium levels should be maintained >4.0 mEq/L before and during therapy 2
- Tablets should not be cut; dose adjustments should be made by changing the prescribed tablet strength 2
Monitoring During Loading Phase
During the loading phase, patients should be monitored for:
- QT interval prolongation
- Bradycardia
- Gastrointestinal side effects (constipation, nausea)
- Neurological effects (ataxia, tremor, paresthesias) 1, 2
Important Considerations and Pitfalls
- Side effects are common (occurring in up to 93% of patients) and often dose-related 3, 4
- Higher loading doses (>1,800 mg/day) have been used in unstable patients with incessant ventricular tachyarrhythmias, but should be reserved for these critical cases 5
- Amiodarone has a narrow therapeutic-toxic range; close monitoring is essential 3
- The long half-life of amiodarone (14-58 days) means that steady state may not be achieved for weeks to months 6
- Drug interactions are significant, particularly with warfarin, digoxin, and statins; dose adjustments of these medications may be necessary 2
Clinical Efficacy
Amiodarone has shown efficacy rates of 76-83% for controlling refractory tachyarrhythmias 7. The electrophysiologic effects begin within the first day of high-dose loading, with progressive increases in ventricular tachycardia cycle length and right ventricular effective refractory period 5.